High-frequency system



Julyl, 1930. R. D. @UNC/1N, JR 1,769,018

Y HIGH FREQUENCY SYSTEM v Filed Feb. 15, 1926 4 Sheet's-Sheet l d4 n i dimmi;

July l, 1930. R. D. DUNCAN, JR

HIGH FREQUENCY SYSTEK 4 Sheets-Sheet .2

Fi'led Feb. l5, 1926 July 1, 1930. R. D. DUNCAN,Y JR A 1,769,018

HIGH`FREQUENCY SYSTE Filed Feb. l5, 1926 4 Sheets-Sheet 3 gnvenloz July l, 1930. R. D. `DUNCAN, JR

HIGH FREQUENCY SYSTEI Filed Feb. 15, 192s 4 sheets-sheet' 4 Patented July 1, 1930 UNITED STATES MBERT D. DUNCAN, JR., 0F EAST ORANGE, NEW JERSEY, ASSIGNOB', BY HESNE PATENT OFFICE ASSIGNMENTS, T0 FEDERAL TELEGRAPH COMPANY, A CORPORATION 0F' CALI- FORNIA.

HIGH-FREQUENCY SYSTEM Application led February 15, 1920. Serial No. 88,279.

My invention relates broadly to the generation of polyphase high frequency4 currents, and more particularly to electron tube apparatus and circuits for the production of polyphase high frequency currentsfor signal transmission systems.

One of the objects of my invention is to provide a type of multi-element electron tube and a system of circuits by means of which direct current may be' converted by the electron tube into polyphase and in particular three phase high frequency current.

Another object of my invention is to provide an electron tube structure and circuits by which means direct current may be converted into polyphase and in particular three phase alternating current in which all even harmonics and all triple frequency harmonies of the fundamental frequency are suppressed.

Still another object of my invention is to provide a transmission and modulation system employing a polyphase electron tube structure and system of circuits.

A further obJect of my invention is to providev a high frequency current generation system in which single phase high frequency current may be converted into polyphase high frequency current for polyphase el'ectric power transmission.

Still another object of my invention is to provide a practical construction of a poly phase high frequency current generator which may be operated from sources of direct current or single phase high frequency current normally available for the supply of polyphase high frequency electrical energy for space radio or wired radio broadcast transmission.

A still further object of my invention is to provide an electron tube structure and circuit arrangement for the production of a revolving electrostatic field from a source of single phase high frequency current which may be utilized by the interposition of related electrodes and interconnecting circuits for deriving polyphase high frequency currents therefrom.

My invention will be more clearly understood from the specification hereinafter following by reference to the accompanying drawings, in which:

Figure l illustrates at a, b, c and d an assembled electron tube generator employed in the system of my invention andthe parts of such generator; Fig. 2 is a side elevation of one of the arrangements of electron tube structure; Fig. 3 illustrates a circuit arrangement for the generation of three phase high frequency energy from a source of single phase high frequency energy employing an electron tube construction in accordance with my invention; Fig. 4 illustrates diagrammatically the construction of an electron tube and circuit arrangement which I provide for the generation of three phase high frequency currents with means in the circuits for balancing out the even harmonics and the triple frequency harmonics; Fig. 5 shows an application of the principle of my invention to the generation of six phase high frequency current; Fig. 6 is a diagrammatic view showing the relation of current flow in the several circuits of the electron tube generator circuit of Fig. 3; Fig. 7 shows a modified circuit arrangement for securing a displacement in phase of voltages derived from a single phase source which are impressed upon the three phase electron tube generating circuit; Fig. 8 illustrates a modified arrangement of electron tube structure and source of three phase high frequency energy by which polyphase high frequency electrical energy may be produced; and Fig. 9 illustrates an electron tube structure and circuit arrangement by which a single phase source of high frequency current is utilized to produce a revolving electric field within the electron tube structure by means of voltages displaced in phase by degrees.

' and transverse.

With the introduction of polyphase high frequency current transmission and reception systems the necessity for a generator of polyphase high frequency electrical energy has become essential. Applications of the polyphase generation system of my invention described herein will be more clearly understood by reference to thefollowing copending applications for Letters Patent: Serial No. 35,212, Robert D. Duncan, Jr., three hase wired radio receiving circuits, filed June 5, 1925 now Patent 1,592,085, dated July 13, 1926; Serial No. 45,131, Robert D. Duncan, Jr., three phase high frequency system, filed July 21, 1925; Serial No. 45,132, Robert D. Duncan, Jr., Samuel Isler, and Salvatore A. Barone, three phase high frequency system, filed July 21, 1925 now Patent 1,669,159, dated May 8, 1928; and Serial No. 45,948, Robert D. Duncan, Jr., duplex radio telephone system, filed July 24, 1925 now Patent 1,591,025, dated July 6, 1926 and Patent No. 1,560,505, issued November 3, 1925 to Robert D. Duncan, Jr., for method of carrier frequency suppression.

Referring to the drawings in more detail the numeral 1 represents the filament of the electron tube system which in normal operation is heated to incandescence and which may be composed of tungsten, thoriated tungsten or any other substance which is normally emplo ed in the manufacture of filament wire. Filament 1 runs longitudinally with the glass container 2, shown here in cylindrical form. Connections 3 illustrated in Figs. 2 and 3 are common with filament 1 and serve to convey the heating current thereto. distance therefrom and concentric therewith, is a latticed wire cylinder divided into four segments 4, 5, '6, 7, having substantially the same areas. These four segments are disassociated from one another by spaces 8 with their longitudinal axes displaced by 90. In the drawings the segments are shown to be of lattice construction, that is, a grid of wires running both longitudinally Any similar type of construction may be employed such as perforated or slotted metal plates. Segments 4, 5, 6, 7, may not be solid construction. Surrounding both filament 1 and segments 4, 5, 6, 7, and at a distance therefrom are three plates 9, 10, 11, which are made of three substantially equal segments of a hollow metallic cylinder concentric with filament 1 and segments 4, 5, 6, 7. Plates 9, 10,11, are solid in construction, are separated from one another by spaces 12 and have their longitudinal axes dis laced by angles of 120. Filament 1, gri -segments 4, 5, 6, 7, and plates 9, 10, 11, are suitably housed and supported in a hermetically sealed glass vessel indicated at 2. Vessel 2 is evacuated and the tube elements are treated so as to Surrounding filament 1 at a` drive of oocluded gases by an of the usual methods. Connections from lament 1 are brought out at 3 3, from rid-segments 4, 5, 6, 7, at 13, 14,15, 16, and from plates 9, 10, 11 at 17, 18, 19.

The electron tube structure thus consists of an evacuated glass vessel 2 supporting and containing a filament 1, surrounding which and concentric with which are, first, four sets of grid-segments 4, 5, 6, 7, displaced from one another b angles of 90, and second, by three sets o plates 9, 10, 11, displaced from one another by angles of 120. Leads for connecting with the two ends of the filament and to each of the grid-segments and to the lates are brought out through the walls o the glass and the joints suitably sealed.

By the tube construction and arrangement of plates 9, 10, 11, and the disposal of the electrodes within the tube, polyphase alternating current may be generated. The arrangement shown in Fig. 5 is for generation of six phase alternating current. It consists of the filament 1 and grid-segment 4, 5, 6, 7 structure of Figs. 1, 2, 3. Instead of three plates there are, however, six plates 20, 21,22, 23, 24, 25 disposed about grids 4, 5, 6, 7,' the same as described for Figs. 1, 2, 3, plates 20, 21, 22, 23, 24, 25, being displaced from one another, however, by angles of 60.

The operation of the tube and associated circuits for generating three phase high frequency current is best ex lained in reference to Fig. 3. In this gure the tube elements are numbered as indicated in Figs. 1 and 2. In addition numeral 26 represents a battery for rendering filament 1 incandescent to the proper degree. One terminal of battery 26 is grounded at 27. The negative terminal is here indicated. 28 represents a source of single phase high frequency current, which supplies energy to circuit 30 through the means of transformer 29. Circuit 30 consists of secondary coil 32 of transformer 29, variable inductance 33, variable capacity 34, and primary coil 36 of transformer 35. Inductively coupled to circuit 30 is a second circuit 31 consistin of secondary 37 of transformer 35, varia le inductance 38 and variable capacity 39. Connected to the two terminals of capacity 34 through connections 13, 15, are the grids 4, 6, of the tube. Connected to the two terminals of capacity 39 through connections 14, 16, are the two remaining grids 5, 7, of the electron tube. Bridged across grids 4, 6, 5 and 7 are respectively, high series connected resistances 40-41 and 42- 43, the midpoints of which are connected to the negative terminals of batteries 44 and 45, the positive terminals of which are grounded at 27. Plate 9 of the tube is connected through connection 17 through capacityt 46 to one terminal of inductance 47, the other terminal of which is grounded at 27 through connection 48. In a similar manner, plates l and 1l are connected through capacities 51 and 51l to one terminal each o' iiuluctances 50 and 52 through connections 18 und 19. The remaining terminals of .iiuluctaiunes and 52 are connected with the grounded terminal of inductance 47 through the common connection 48. It will be noted that inductances 47, 50 and 52 are connected in the well known Y or star, three phase manner. Plates 9, 10, and 11 receivetheir requisite high posltive voltage from source 49, here shown as a battery, the negative terminal of which is grounded at 27. The positive terminal is connected through the choke coil 200, and therethrough to the high frequency choke coils 201, 202 and 203, respectively, to plates 9, l0, 11. The plate 54 of electron tube 55 also receives its high positive volta e from battery 49 through choke 200. he filament 56 of the tube 55 is grounded at 27. Grid 57 is connected through the secondary 58 of speech input transformer 59, and through biasing battery to the grounded terminal of 'filament 56. The primar 61 of transformer 59 is connected in serles with microphone 62 and battery 63. It will be 0bserved that tube 55 with its associated speech input apparatus serves merely to effect modulation by voice or otherwise, of the high frequency output of tube 2 by one of the well known methods of modulation. Inductively coupled to inductances 47, 50, 52, are secondary inductance coils 64, 65, 66, each of which preferably has in series variable inductances 67, 68, 69. Inductances 64, 65, 66, 67, 68, 69, are interconnected in A in the three phase manner. At the apexes of the A connections 70, 71,- 72, are made through variable capacities 73, 74, 75, to the ultimate load for tube 2, here indicated as a three phase transmission line 76.

In Fig. 3 as Well as inthe other figures, circuit connections to ground 27 bring s uch points to the same potential and, therefore, serve as a oint of common connection.

Single p ase high frequency source 28, by virtue of coupling at transformers 29 an 35 will establish currents in circuits 30 and 31. With suitable adjustment of these two circuits, with the proper coupling at transformer 35, and further, with. circuit 31 adjusted to be substantially inpresonance with the frequency of source 28, the currents in circuits 30 and 31 ma be made to differ in time phase by gince the voltage developed across la capacity is given by idt,

where C is the capacitance of the condenser, 1I the traversing current and dt the differential time, the voltages devel ed across capacities 34 and 39 must also 90 out 'of phase.r4 By means of connections 13-15 and 14-16 these quadrature voltages are impressed on the grids 4-6 and 5--7 within the evacuatedy vessel 2.

Under these conditions there is then produced between and around grids 4,'5, 6, 7, which practically constitute the armatures of two condenser-s, in accordance with fundamental electrical theory, a rotating electric field, which revolves in synchronism with the frequency of source 28, the effective axis of revolution being substantially the filament 1 of the tube. If the circuits 30, 31, are properly adjusted the revolving field will be circular, that is, the field will have the same value for all oints of its angular dislacement, which 1s a preferred condition.

he electric field rotatin about filament 1 will, for example, when 1t is directed from cally in Fig. 6 ((L); Assuming that the field g revolves in a clockwise direction, 120 time degrees after it is such as to cause an increase in plate current of plate 9, it will cause a similar increase in the current to plate 10, as shown in Fig. 6 (b). Likewise 120 time degreesafter this condition, it will cause a simllar increase in current to plate 11 as shown in Fig. 6 (c). When the action of the field is to cause a decrease in the flow of electrons to lates 10 and 11, a decrease in the current owing therefrom will result. Therefore, under the action of the revolving electric field of grids 4 6, 5-7, and in accordance with the well known laws gov- .erning the flow of electrons in an evacuated space between a hot cathode and cold positively charged anodes, in the presence of Varying interposed charges in the field between the hot cathode and the cold anodes, the direct current as drawn from source 49 will be converted into alternating current in the branches 46-47, 49-50, 51-52, of the same frequency as the driving source, and because of the angular displacements of plates 9, 10, 11, Within the tube, the three alternating components of the plate currents flowing in circuits composed of elements 46-47, 49.-50 and 51-52, will differ in time phase by 120. A three phase electron tube generator of high frequency currents is thus obtained. In Fig. 3 due to the coupling between coils 47-64, 50-65 and 52-66 and tothe A connection of coils 64-67, 65-68 and 66-69, three phase currents are established in the transmission lines 76. V- Y Another way of viewing the action within the tube is that the rotating electric field produces a rotatin stream or cloud of electrons to revolve a ut the filament Las an axis. When the electronic stream is made to impinge upon any one of the three plates 9, 10 11, a current will pass across the evacuate space to filament 1. The angular displacin b 120 of the three plates 9, 10, 11, aroun filament 1, by virtue of the action of the rotating electron stream provides a means for generating alternating currents in the circuits connected with plates'9, 10, 11, which will differ in time phase by 120.

The function of high resistances 40- 41, 42 43, which may or may not be required is to afford a leakage path to the grounde filament 1 for the excess electrons which may collect on grids 4--6 and 5 7. Batteries 44 and 45 which may or not be required, serve to rovide the proper negative biasin voltage or the grids 4-6, 5 7.

Mo ulation of the output of tube 2 is effected by means of tube and associated apparatus. This tube, in the well known manner, functions as an audio or speech frequency amplifier, the audio frequency voltage developed over the chock coil 200 being a plied in effect in series with the voltage of) source 49 to plates 9, 10, 11. Condensers 46, 49 and 51 in accordance with usual procedure have a sufficiently high reactance at audio frequencies to block the flow of audio frequency current from the aths containing them. High frequency c oke coils 201, 202 and 203, together with capacities 46, 49, 51, in the usual combination form a filter for separating out the high frequency alternating and continuous components of the current to plates 9, 10, 11.

The circuits and tube shown in Fig. 5 are foi` the production of six phase high frequency current in the six phase load indicated in its entirety by 77. The plates 20 21, 22, 23, 24, 25, are connected in the usual double Y or double start six phase manner through circuits 78, 79, 80, 81, 82, 83, and common connection 84 to ground 27. Only the alternating components of the plate circuits are shown in Fig. 5. The plates obtain their requisite high positive voltage from the same source through high frequency choke coils as shown in Fig. 3.

The arrangement of circuits 30, 31 of Fig. 3, for obtaining two alternating voltages differinvl in time phase by substantially 90 with which to roduce a revolving electric field is one which has been found to yield both flexibility and stabilit of operation. There are other methods o accom lishino this end, however, which are effective with the tube structure shown in Figs. 1, 2, 3, 4 and 5, and with the tubestructure of Figs.

polyphase tube of suitable internal structure. 1

Since an electron tube is inherently a voltage o rated device, the circuit arrangement of i 7 may be employed. In Fig. 7, 28 (as in ig. 3) represents a source of single phase high frequency current operating into circuit 85, consisting of variable inductance 86, variable resistance 87, and variable capacities 88 and 89 connected in series. If R represents the resistance of that portion of resistance 87 included between variable ta 90 and common connection 91, and C andh respectively, the capacitance of capacity 88 and (21- x frequenc the voltages developed across these will equal if R=wi0 fundamental electrical laws will be substantially 90 out of phase. Through connections 13 15, and 14-16 extending to grids 4 6, and 5 7, as shown in Fig. 3, a revolving electric field is produced within the poly or three phase tube.

I have described particular methods for the production of revolving electric fields from two alternatin voltages out of phase bIy 90. It is possi le to obtain revolvin e ectric fields under other conditions o hase displacement. The essential feature 1s that the phase difference in electrical degrees between the producing voltages be substantially the saine as the an lar displacement between the grids whic produce the revolving field. For exam le, with the tube structures of Figs. 1 to 5 inclusive the pairs of rids 4 6, 5 7, are displaced by 90, whic is also the phase angle between the producing voltages developed over capacities 34, 39.

In the tube structure of Fig. 8 the grids 92, 93, 94, are displaced by angles of 120. The remaining filament and plate elements for the tube are the same as the tube of Figs. 1 to 5 inclusive. The tube arran ement and circuit of Fig. 8 is intended or three phase hi h frequency current generation, though t e six phase plate structure of Fig. 5 may be used for six phase generation. To produce a revolving electric field between grids 92, 93, 94, the voltages impressed between the same must differ iii time phase by 120. Any suitable arrangement of circuits for obtaining three phase voltages may be used. For example, in Fig. 8, 101 re resents a suitable type of three phase hi Il frequency current generator, of the kin shown in my Letters Patent and in accordance with 1,578,881, dated March 30, 1926. Generator 101 operates into the three A connected. primary inductances 95, 96, 97. Inductively coupled to the latter are three Y connected inductances 98, 99, 100, the common terminal of which is grounded at 27 through biasing battery 102 poled yso that the positive terminal is grounded. The free terminals of inductances 92, 93, 94, produce around and between the same a revolving electric field or stream of electrons. The plates 9, 10, 11, through connections 17, 18, 19 may be connected in the same manner s own in Fi 3. v

Ihe revolving field, similar to that of Figs. 1 to 5, rotates 1n synchronism with the frequency of the voltage of the source 101. If E represents the maximum intensity of the field produced by the 90 tube structures of Fi s. 1 to 5, the maximum intensity of the fiek? of the tube structure of Fig. 8 will be 1.5E, as may be determined from a mathematical consideration of the amplitude and phase of the voltages involved.

The tube structure and circuit arrangement shown in Fig. 9 discloses a means for lgenerating three phase current from the effects of a revolving4 electric field, in turn produced by voltages displaced in phase by 45. In Fig. 9, 28 1s a source of single phase high frequency current which operates into circuit 103 made u of variable inductance 104, variable capacity 117 and the primary inductances 109, 110, 111, 112, of transformers 105, 106, 107, 108. Secondary 113 and 114 of transformers l105 and 106 are, respectively, connected in series with capacity 118 and resistance 119, and capacity 120 and resistance 121. Secondary 115 is connected in series with resistance 122;` secondary 116 is connected in series with inductance 123 and resistance 124. The capacities, resistances and inductances are preferably variable. In the tube 2 there are contained as before, filament l, and

plates 9, 10, 11, with output connections- 17 18, ,19. The grid structure of the tube of Fig. 9 consists of four pairs of grids 125-129, 126-130, 127-131, 12S-132, the

adjacent grids being displaced by angles of 45o from eah other. Connections 133, 137, extending from 125-129 connect with the opposite terminals of resistances 119. In a similar manner, leads 134-l38, 135-139, 136-140 connect respectively, with the two terminals of resistances 121, 122 and 124. Highresistances 141, 142, 143-144, 145- 146, 147-148, are connected in series respectively, between the grids 125-129, 126- 130, 127-131, 128-132. The midpoints of these resistances are connected through the common connection 150 to the negative terminal of battery 149, the positive terminal of which is rounded at 27. The output connectionsl 18, 19, may be associated with circuits as shown in Fig. 3. The fitlaQnIlent 1 of tube of Fig. 9 is grounded a The driving voltages induced in each of secondaries 113, 114 115, 116, lag the magnetic flux established by the current in series connected primaries 109, 110, 111, 112, by substantially 90. With the proper ratio of reactance of calpacity 118to reslstance 119, the current in t e circuit 113-118-119 will lead the driving voltage of that circuit by substantially 90. The volta e developed over resistance 119 will be in hase with the current and will also lead the riving-volta e by 90. With suitable adjustment of t e reactance of capacity 120 and resistance 121, the current in circuit 114-120-121 will leadthe driving volta ein this circuit by 45. The volta e deve oped over resistance 121 will, there ore, also lead the drivin voltage by 45 or lag the voltage develope over resistance 119 by substantially 45. The current in circuit 115-122 is virtually in phase with the driving voltage induced in secondary 115.- The voltage developed over resistance 122 therefore lags the voltages developed over resistances 119 and 121, respectively, by 90 and 45. With suitable adjustment of the reactance of inductance 123 and resistance 124, the current in circuit 116-123-124 will lag the driving voltage induced in 116 by substantially 45. The voltage developed over resistance 124 since it is in phase with the current will therefore lag the voltages developed over resistances 119, 121, 122, and 124, respectively, by 135, 90 and 45.,

By means of the circuit connection and the tube structure of Fig. 9 a revolving electric field is produced within and around grids 125, 126, 127, 128, 129, 13o, 131, 132. It may be shown that the maximum value of the revolving electric field is twice that obtained with grids displaced by 90. With the output connections 17, 18, 19, from the three .plates 9, l0, 11, interconnected with a three phase circuit and a source of direct current supply, such as is shown in Fig. 3, three alternatlng currents will be established which differ in time phase by substantially 120, that is to sa a three phase electron tube generator is o tained.

The tube structure and circuits of Fig. 9 provide a very eliicient means of three phase current eneration. The principle illustrated in ig. 9 may be further extended and a revolving field obtained by voltage displaced by 30, 22.5, 15, 12, 10, or theoretically by any angle divisible into 360, the only essential requirement is that the angular displacement between the grids of the tube be the same as thelphase angle between the volta es which go to produce the revolving geld. My invention is therefore susceptible to a number of modifications.

The tube structure shown in Fig. 4 consists of a filament 1, grids 41-61', 51-71, similar to grids 4-6, 5--7 of Figs. 1, 2, 3, but here shown as sections of a plane instead of a cylinder, and two sets each consisting of three plates, 9, 10, 11" and 9 10', 11', also sections of planes instead of a cylinder. The grids are dis osed around the filament in a 90o relationship; the plates are displaced from each other by 120. The filament 1 as before, is heated to the proper degree of incandescence by means of battery 26, the negative terminal of which is grounded at 27. Grids 41, 51, 61, 71, through leads 131-151 and 141-161 are assumed to be connected with condensers simliar to 34 39 of Fig. 3 to obtain two volta' es out of phase by 90 with which to pro uce a revolving electric field around grids 41-62 51-71. Plate 9 through lead 17 is connected through capacity 151, and inductance 152 to the ground 27 through common connection 153. Plate 9 through lead 17 is likewise connected through capacity 154 and inductance 155 to ground 27 through common connection 153. In a similar manner, plates 10 and 10 through leads 18 and 18 are connected respectively, through capacities 156, 158 and inductances 157 and 159 to ground 27 through common connection 153. lThe same method of connection holds for plates 11, 11', throu h leads 19" and 19 respectively, throug capacities 160, 162, and inductances 161, 163, to ground 27 through common connection 153. Plates 9, 9', 10, 10', 11, 11 receive their high positive voltage from source 164, here represented as a D. C. generator of which the negative terminal is grounded at 27, through high frequency choke coils 165 and leads 166. It will be noted that the inductances 155, 157, 161, and 152, 159, 163, considered in order of three named, are Y connected with a common terminal grounded, in the three phase'manner, and function as the output inductances of the circuits containing plates 9 10', 11 and 9, 10, 11. Inductively coupled with inductances 155-152, 157--159, 161-163, are respectively, inductances 167 168, 169, which are also connected in Y through common connection 170. These latter inductances operate into the final load, here represented as a three phase transmission line 177, through variable inductances 171, 172, 173, and variable capacities 174, 175, 176.

By the principles outlined herein, the revolving electric field produced by the grids 41, 51, 61, 71, will convert the direct current drawn from source 164 into three phase alternating current effective in the output plate circuits of the tube. The frequency of the three phase current is the same as that of the single phase source which produces the voltages utilized for obtaining the revolving electric field of rids 41--61, 51-71. Now the fundamental aw of the three electrode electron tube (in this case the three electrodes comprising the filament, one grid and one plate), is well known to approximate the square relationship, that is, the plate current varies substantially as the square of the voltage applied between the grid and filament, for a given applied plate voltage. Under this condition it may be proved and is well known that if the grid volta e is alternating, that is, a sinusoidal function, the outputplate current in addition to the fundamental frequency component will contain all the even harmonics thereof. The balanced plate circuit connection of Fig. 4 is fundamentally similar to the push-pull connection well known in the radio art, by which means the even harmonies are in opposition or balance out in their effect upon the final output circuit. In Fig. 4 this balancing effect is obtained by virtue of the connections between the paired gil- Qlll, lOl/lO//l ll-ll/, and the usual differential placing of inducrames 155-152, i57i59, lei-16a, which are respectively, coupled to inductances 167, 168, 169, so that no even harmonic frequency currents will be induced in the latter. Furthermore, it is known in the electric power I amplifier. Due to the Y connection of inductances 167, 168, 169 of Fig. 4, the triple frequency harmonics are balanced out of the load or lines 177.

The tube structure and circuit arrangement disclosed in Fig. 4 constitute a new means for generating three phase high frcquency current which is free from all even harmonicsv and from the triple frequency harmonics and all multiples thereof. The remaining harmonics may, therefore, be of the order 5th, 7th, 11th, 13th, etc.,usually of rapidly diminishing amplitudes.

The elimination or partial elimination of harmonics is very essential in multiplex transmission, either for space or wired radio, as otherwise with the displacement of fundamental frequencies to avoid interchannel interference it is virtually impossible to simultaneously avoid beating between some of the various harmonic frequencies.

As has heretofore been pointed out, the polyphase high frequency generator of my invention has numerous applications. The apparatus may be compactly arranged in a yunit which is readily installed in a power llO lant for super-imposing polyphase high requency energy on polyphase transmission lines emanating from the power plant 1n a wired radio broadcasting system. Likewise, the apparatus may be compactly installed in a space radio broadcasting station in systems of cari-ier wave suppression in which polypliase signalin energ is employed as described in one o the a orementioned copending applications for Letters Patent.

While I have described my invention in certain preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon the invention are intended other than those imposed by the scope of the appended claims.

What I claim and desire to secure by Letters Patent of the United States is as follows:

l. In a system for the generation of polyphase high frequency currents, the combination of a source of alternating current, and

means for obtaining voltages differing in time phase from said source comprising an electron tube system, means for producing' a revolving electric field in said electron tube system, circuits terminating in said revolving electric field, each of said circuits including a series connected inductance and capacity, means for balancing each circuit and a polvphase high frequency system connected with each of said circuits.

2. In a system for the generation of polyphase high frequency electrical energy, the combination of a source of alternating current, and means for deriving voltages disv placed in phase from said source comprising an electron tube system, having means for producing a revolving electric field therein, a pluralit of circuits terminating in said revolving e ectric field, a series connected inductance and capacity included in each of said circuits, and a polyphase high frequency system coupled to each of said inductances.

3. In a system for the generation of polyplurality of circuits terminating in said re-.

volving electric field, a series connected inductance and capacity connected in said circuit-s, and a polyphase high frequency circuit coupled with the inductances in each of said circuits.

4. Ina system for the generation of high frequency polyphase current, a source of alternating current, an electron tube system having a plurality of electrodes therein, `means for producing a plurality of voltages differing in phase for exciting said electrodes in differing time phase lfor producing a revolving electric field around said elecnected across selected ones of said imped-I ances, and connections between said' source and each of said tuned circuits.

5. In a system for the generation of high frequency poly hase electrical. energy, the combination o a voltage source, circuits connected'with said source for derivino' a plurality of voltages therefrom, each differing in time phase, :an electron tube system including a source of electrons, a plurality of independent grid electrodes surrounding said source of electrons, a plurality of independent plate electrodes surrounding said grid electrodes, a polyphase circuit interconnecting said plate electrodes, means for impressing said voltages differing in time phase upon said grid electrodes for producing a revolving electric field, impedanclcs connected in shunt with selected sets of said grid electrodes, and independently adjustable circuits connected to said impedances and to said source.

6. In a system for the generation of polyphase high frequency electrical energy, the combination of a voltage source, means for deriving a plurality of voltages differing in time phase from said source, an electron tube system having a source of electrons therein, a plurality of grid electrodes surrounding said source of electrons, circuits for impressing said voltages of differing time phase on said grid electrodes for producing a revolving electricl field Within said electron tube system, a pluralit of plate electrodes surrounding said gri electrodes, divided paths for current flow connected to each of said plate electrodes, and a; polyphase circuit coupled to each divided path.

7. In a system for the generation of polyphase high frequency electrical energy, the combination of a voltage source, means for deriving voltages from said source differing yin time phase With respect to each other, an electron tube system including a source of electrons, a plurality of sets of grid electrodes corresponding in number to twice the number of said voltages' differing in time phase for producing a revolving electric field, a plurality of plate electrodes surrounding said grid electrodes and corresponding to the number of phases of high frequency current which it is desired to produce, circuits interconnecting said late electrodes for the generation of polyp ase high frequency electrical energy, each of said circuits including a pair of differentially coupled inductances for balancing out the even harmonic. frequencies.

y 8. In a system for the generation of polyphase high frequency electrical energy, the

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combination of a voltage source, means for deriving voltages therefrom differing in time phase, an electron tube system including a source of electrons, a plurality of sets of grid electrodes surrounding said source of electrons and corresponding in number to the number of differing time phase voltages impressed thereon, a plurality of plate electrodes surrounding said grid electrodes and corresponding in number to the number of phases of the polyphase energy generated'by said electron tube system, circuits interconnecting said plate electrodes, said circuits each including a pair of differentially coupled inductances whereby polyphase high frequency electrical energy may be generated therein and even harmonic frequencies balanced out.

9. In a system for the generation of polyphase electrical energy, the combination of a voltage source, means for deriving voltages therefrom differing in time phase, an electron tube system, a so'urce of electrons therein, a plurality of grid electrodes surrounding said source of electrons, a plurality of plate electrodes surrounding said grid electrodes, circuits interconnecting each of said plate electrodes, a pair of differentially coupled inductances included in each of said circuits, and means whereby a revolving electronic stream is produced around said source of electrons for generating polyphase electrical energy at a fundamental frequency While balancing out selected harmonic frequencies.

10. In a system for the generation of three phase high frequency currents, the combination of a source of single phase high frequency current, circuits connected with said source for deriving voltages differing in time phase, an electron tube system having a source of electrons, a plurality of sets of grid electrodes surrounding said source of electrons, connections for impressing said voltages across said electrodes for producinga revolving electronic field, a plurality of plate electrodes corresponding in number to the number of phases of current generated by said electron tube system, and independent circuits connected with each of said plate electrodes for the generation of three phase electrical energy said circuits each including a pair of differentially coupled inductance elements for balancing out selected harmonic frequencies.

11. In a system for the generation of three phase high frequency currents, the combination of a source'of high frequency electrical energy, means for deriving voltages differing in time phase from said source of energy, an electron tube system having a source of electrons, a set of grid electrodes surroundspending in number to the number of phases generated by said electron tube system, circuits interconnecting said plate electrodes, and a three phase circuit coupled with all of said circuits whereby a revolving electronic field impinges on said plate electrodes for the generation of three phase electrical energy in said circuits and a pair of differentially cou led inductances included in said circuits or opposing the effects of even harmonic frequencies in said circuits.

12. In a system for the generation of olyphase high frequency currents, the com ination of a source of electrical energy, means for obtaining voltages differing in time phase from said source, an electron tube system, means for producing a revolving electric field in said electron tube system, circuits terminating in said revolving electric field, a polyphase circuit connected with said aforementioned circuits, means for generating polyphase electrical energy in said circuits, and means connected with each of .said circuits for the elimination of even harmonics from said polyphase circuit cornprising pairs of inductively coupled circuits connected to oppose the generation of predetermined harmonic frequencies.

13. In a system for the generation of three phase high frequenc currents, the combination of a source of igh frequency current, means for obtaining voltages differing in time phase from said source, an electron tube system, means for producing a revolving electric field in said electron tube system, circuits terminating in said revolving electric field, a three phase electric power distribution system connected with said circuits, and a pair of balanced circuits connected with each of said circuits for eliminating Athe even harmonics and all triple frequency harmonics of the fundamental frcquency of said high frequency current source from said three phase system in the generation of three phase currents.

14.-. In a system for the generation of polyphase high frequency currents, the combination of a source of high frequency electrical energy, means for obtaining voltages differing in time phase from said source, an electron tube system, means for producing a revolving electric field in said electron tube system, balanced circuits each including inductance and capacity elements, said circuits terminating in said revolving electric field, a polyphase system coupled with the inductance elements of said balanced circuits, said balanced circuits providing means for eliminating even harmonics in said polyphase system.

15. In a system for the generation of high frequency three phase electrical energy, the combination of a source of high frequency current, circuits connected with said source for deriving a plurality of voltages there- 'electrical circuit connected between each phase of said electrical circuit and a plate electrode in each of said sets of plate electrodes for impressing three phase electrical current on said three phase load circuit free of even and triple fr uency harmonics.

16. `In a system for t e generation of high frequency polyphase electrical energy, the combination of a high frequency voltage source, circuits connected with said source for deriving a plurality of voltages there from, each differing in time phase, an electron tube system'including a source of electrons, a (plurality of pairs of grid electrodes surroun ing said source of electrons, branch circuits coupled to said source, potentiometers connected with each of said branch circuits, connections from said potentiometers for impressing voltage across each pair of grid electrodes for producing a revolving electronic lield, a plurality of Sets of plate electrodes surrounding said grid electrodes, a polyphase electrical load circuit, connections between each phase of said electrical circuit, and an electrode in each of said sets of plate electrodes for the production of 'polyphase\current free of even harmonics and triple frequency harmonics. y

17. In a system for the generation of polyphase high frequency energy, the combination of a source of voltage, an electron tube system comprising an evacuated vessel, a source of electrons therein, a plurality of pairs of grid electrodes mounted diametrically opposite each other on opposite sides of said source of electrons, potentiometers connected across said voltage source, connections between selected points on said potentiometersto said grid electrodes for impressing a voltage across one pair of said grid electrodes differing in time phase from the voltage impressed across another pair of said grid electrodes for producing a revolving electronic field about said electrodes, a plurality of plate electrodes surrounding said grid electrodes and corresponding in number to the number of phases of polyphase current generated by said electron tube system, a pol phasecircuit, and connections between eac phase of said polyphase circuit, and each of said plate electrodes for the generation of polyphase energy in said polyphase circuit.

18. In a system for the generation of polyphase electric currents, the combination of ka source of voltage, an electron tube Asystem comprisin an evacuated vessel, a source of electrons t erein, a plurality of pairs of grid electrodes positioned on diametrically op osite sides of said source of electrons, a p urality of branch circuits connected with said voltage source, connections between each of said branch circuits, and a potentiometer, connections between selected points on said potentiometer and a pair of said grid electrodes for impressing voltage across the respective pairs of' grid electrodes dilfering in time phase relation for the production of a revolving electronic field, a plurality of plate electrodes, a polyphase circuit, and connections between said plate electrodes and each phase of said polyphase circuit for the gen eration of polyphase current in said polyphase circuit.

19. In a system for the generation of polyphase alternating currents, the combination of a source of voltage, an electron tube system comprising an evacuated vessel a source of electrons therein, a plurality of pairs of grid electrodes positioned on diametrically opposite sides of said source of electrons, a plurality of branch circuits connected with said voltage source, resistances.

connected in shunt with each of said branch circuits, connections between the opposite terminals of said resistance and a pair of said grid electrodes, a connection between said resistances and said source of electrons for normally biasing said grid electrodes at a certain voltage with respect to said source of electrons, each of said branch circuits being arranged to im ress voltages across said grid electrodes di ering in time phase relations for establishing a revolvin electronic field within an evacuated vesse a plurality of plate electrodes surrounding said grid electrodes, a polyphase electrical circuit, and connections between said plate electrodes and said polyphase circuit for the generation of polyphase currents therein.

20. In a system for the generation of polyphase high frequency electrical energy, the combination with a voltage source, an electron .tube system including a source of electronsa pluralityof grid electrodes surrounding said source of electrons, said grid electrodes extending adjacent said source circuit, and means coupled with each of said phases of said electrical circuit and connected with a plate electrode in each of said groups of electrodes for im ressing polyphase electrical energy on sai polyphase circuit.

21. In a system for the generation of three phase high frequency current, a source of single phase alternating current, circuits electrically connected with said source providing means for developin two volta es substantially equal in amphtude and 1ffering in time phase by substantially 90 degrees, an electron tube system comprisin an evacuated vessel enclosing a filament, an sets of grids and plates, said plates bein three in number and disposed around an at a distance from said filament, and angularly displaced around said filament by substantially 120 degrees, connections 4from each of said plates to output inductances interconnected in a three phase manner, additional connections to each of said three plates for providing continuous voltage thereto, and additional inductances coupled to said out ut inductances and interconnected in a tliree phase manner for the development of a fundamental frequency free from selected harmonic frequencies.

22. In a system for the generation of three phase high frequency current, a source of single phase high frequency current, circuits electrically associated with said source providing means for developing two voltages substantially equal in amplitude and differing in time phase by substantially 90 degrees, an electron tube comprising an evacuated vessel enclosing a filament and sets of grids and plates disposed on diametrically opposite sides of said filament, said plates consisting of two groups each in number of hree, each of said groups of three plates being disposed around and at a distance from dierent portions of said filament, the individual plates of each of said groups of three being angularl displaced around said different portions o said filament by substantially 120 degrees, connections from each plate of one of said groups of three plates to output inductances interconnected in three phase Y, and connections from each plate of the second of said groups of three plates to additional output inductances interconnected in three phase Y, said first and additional output inductances being interconnected in a balanced manner for the production of polyphase currents of a fundamental frequency free from selected harmonic frequencies.

23. In a system for the generation of three phase high frequency electrical energy, the combination of a source of single phase alternating current, means for obtaining voltages differing in time phase from saidy source, an `electron tube system comprising an evacuated vessel and therein a source of i electrons, a plurality of sets of grid electrodes Positioned on diametrically opposite sides o said source of electrons, circuits for impressing said voltages differing in time phase between opposing pairs of said grid electrodes for producin a rotatin electric field between and aroun said grid e ectrodes and around said source of electrons, a plurality of sets ofplate electrodes positioned on diametrically opposite sides of said source, each set corresponding in number to the number of phases, impedance circuits disposed in shuntwith each set of said rid electrodes, and output circuits connecte to each of said plate electrodes for the development of polyphase currents, and means for suppressing all even and triple frequency harmonics of the fundamental frequency from said output circuits.

24. In a system for the generation of polyphase electrical energy, a source of alternating current, circuits connected with said Source for obtaining a plurality of voltages differing in phase, an electron tube system comprising an evacuated vessel, and therein a source of electrons, a plurality of grid electrodes positioned around said source of electrons means for impressing saidl plurality of voltages differing in phase on said plurality Of grid electrodes for producing a rotating electric field around said source of electrons, a plurality of sets of plate electrodes corresponding in number to the number of phases of the polyphase generation system and positioned around said grid electrodes to receive electrons from different portions of said source of electrons, impedance circuits connected across each set of said grid electrodes, and output circuits connected with each plate of said lurality of sets of plate electrodes for the evelopment of pol hase currents therein.

25. n a system for generating polyphase alternating current, a source of single phase alternating current, an electron tube system consisting of an evacuated vessel and therein a hot cathode for the emission of electrons, a plurality of grid electrodes surrounding said hot cathode, a plurality of plate electrodes surrounding said grid electrodes, impedances connected across selected groups of said grid electrodes, and output circuits connected with said plate electrodes, the potential drop across said impedances developing a rotating electric field between and around said grid electrodes for influcncin the flow of electrons from said hot catho e to said plurality of plate electrodes for generating polyphase alternating currents in said output circuits.

26. In a system for the generation of polyphase alternatin current the combination of an electron tu comprising an evacuated vessel and therein a source of electrons, and a plurality of groups of grid and plate electrodes disposed on diametrically opposite sides of said source of electrons, resisters shunting the oppositely positioned grid electrodes, said electrodes operating to maintain a rotating electric field Within said electron tube and a polyphase circuit connected to said plate electrodes for the generation of polyphase currents therein under control of said rotating electric field.

27. ln an electric circuit the combination of an electron tube comprising an evacuated vessel and therein a source of electrons, and a plurality of groups of grid and plate electrodes distributed concentrically about said source on diametrically opposite sides thereof, impedances shunting sets of said grid electrodes, said electrodes operating to maintain a rotating electric field Within said electron tube for influencing the flow of electrons to said grid and plate electrodes and a polyphase circuit connected to said plate electrodes for the generation of )olypliase currents therein under control otl said rotating electric field.

28. In a system for generating three hase alternating current comprising in com ination a source of single'phase alternating current, an electron tube system consisting of an evacuated vessel and therein a hot cathode for supplying electrons, a plurality of grid electrodes positioned around said hot cathode, three plate electrodes positioned symmetrically around said grid electrodes, and output circuits associated with said plate electrodes, said grid electrodes being supplied with energy from said single phase source for maintaining a rotating electric field between and around said rid electrodes for influencing the low o electrons from said hot cathode to said grid and plate electrodes for generating three phase'alternating current in said output circuits.

29. In a system for the generation of polyphase alternating current the combination of an electron tube comprising an evacuated vessel, a source of electrons therein, and a plurality of electrodes disposed on diametrically opposite sides of said source, impedances connected in shunt with selected groups of said electrodes, circuits interconnecting selected ones of said electrodes for maintaining a rotating electron stream within said electron tube and a polyphase circuit connected with other selected groups of said electrodes.

30. In a system for generating three phase alternating current comprising a source of single phase alternating current, circuits connected therewith for deriving two voltages of substantially equal amplitudes and differing in phase by substantially 90 degrees, an electron tube system comprising an evacuated vessel and therein a hot cathode for supplying electrons, two pairs of grid electrodes With the electrodes of each pair positioned on diarnetrically opposite sides of said liet cathode, connections for impressing said two voltages differing in phase by substantially 9i) degrees respectively between each ci? said pair of grid. electrodes, three plate electrodes displaced around said grid electrodes by 120 degrees, impedances connected in shunt across pairs et' said grid electrodes, a polyphase circuit connected with said plate electrodesd RBERT DUNCAN, Je. 

